Hydrocarbon oils



nrnnocannon one Joachim Dazzi and loseph E. Fields, Dayton, Ghio, as-

signors to Monsanto Chemical Qompany, St. Louis, Mo., a corporation of Delaware No Drawing. Application November 7, 1952, Serial No. 319,429

2 Claims. (Cl. 252-56) This invention relates to antifoaming hydrocarbon oils and relates more particularly to hydrocarbon oils containing small amounts of polymeric itaconates as antifoaming agents.

The problem of foam inhibition is one of major importance to all industries employing hydrocarbon oils under foam-inducing conditions. While most oils will foam to some extent due to vigorous agitation and aeration in a running engine, foaming becomes a problem only when loss of oil occurs by foam seepage or when so many air bubbles are present in the oil that proper lubrication of bearing surfaces is impeded. Foaming is often experienced with dry sump engines in which there is employed a scavenger pump for collecting oil from various engine parts and returning it to the lubricant reservoir. Here air may be collected along with the oil and deposited in the reservoir. The design and operation of aircraft engines is such that foaming occurs more readily in this type of engine than it does in automotive engines.

Foam and froth in hydrocarbon oils, however, is not due solely to engine design. Although location and design of the oil pump, oil sump and oil lines as well as modification of other mechanical features may retard foam development, when certain oils are employed with high speed engines, mechanical control, alone, does not sufilce. Here, the nature of the crankcase oil is often the prime factor in foaming difficulties. The heavier the grade of the oil or the higher the viscosity of the oil, the more difficult it is to avoid foaming. Heavy grade oils, such as those employed in high-speed diesel and spark ignition engines operating under severe conditions are particularly susceptible to foaming. The heavy oils hold bubbles very firmly so that when foam is formed, it is very persistent.

New developments in engine construction have constantly demanded lubricants having properties not possessed by refined hydrocarbon oils. Improved properties are now generally imparted to lubricants by the use of additives. For example, in order to satisfy the lubrication requirements of hypoid gears, materials which impart extreme-pressure lubricating properties are now generally added to gear lubricants. In most cases, however, the improvement attained in an oil by the use of additives is made only at the expense of increasing its susceptibility to foam. Thus, while the demands of modern engine design for extreme pressure lubricants, for anticorrosive lubricants, for lubricants of increased viscosity and low pour-point and good detersive properties have been met by the formulation and use of numerous chemicals which give these desirable properties to oils when admixed therewith, the use of such additives makes the treated oils particularly susceptible to foaming. While light-grade oils, e. g., SAE grade oils are often non-foaming under the most severe conditions, when there are employed with these oils one or more additives such as viscosity index improvers, extreme pressure resisting improvers, pour-point depressors, etc., the resulting improved oils do not retain their non-foaming characteristics and are frequently even 2,727,006 Patented Dec. 13, 1955 more susceptible to foaming than are the heavy-grade oils.

Hence, with the development of new high-speed engines and the provision of the new additive-type lubricants, the problem of foaming has assumed major importance. Attempts to solve the problem by defoaming existing oils, c. g., by submitting oils to heat-treatment, absorption processes, filtering steps, etc., have proved of but-little value. The most practical solution to this problem has been made by the use of antifoam additives.

Now we have found that foaming of hydrocarbon oils is effectively retarded and even completely inhibited when there is added to such oils a liquid polymer selected from the class consisting of polymeric dibutyl itaconate, polymeric diamyl itaconate and the copolymer of dibutyl itaconate with diamyl itaconate. Such itaconate polymers are readily obtainable by methods known to the art, e. g., by heating dibutyl itaconate or diamyl itaconate or diamyl itaconate or mixtures of the same in the presence of a peroxidic compound as catalyst until polymerization has taken place, and then, if necessary, separating the polymeric itaconate from any diluent, unreacted monomer or excess of catalyst by distillation.

A number of antifoam additives, i. e., antifoaming agents, foam depressing agents, foam depressants, antifrothers or foam suppressors, are known; but in prior art their use has been attended with numerous diificulties. Among disadvantages of such known additives are chemical reactivity with the lubricant or other oil additives, corrosive effect, susceptibility to decomposition upon heating, instability when exposed for long periods of time to ordinary atmospheric conditions, high cost, etc.

The present itaconate polymers possess very high antifoaming elficiency and may be employed in only very low proportions, i. e., in amounts generally less than 1.0 per cent by weight of the oil. From 10 to parts of the polymer per million parts of the oil is preferred, depending upon the nature of the oil. Heavy oils and oils containing foam-inducing adjuvants require more of the polymers. While the antifoaming efiect of the present itaconates is obtained when they are employed in small concentrations, the polymers may be incorporated into the hydrocarbon oil in amounts of, say, up to 50 per cent by weight to give concentrates. Oils containing such high proportions of the polymers may be marketed for use as lubricant additives whereby addition of small amounts of the concentrate to hydrocarbon oils can be so regulated as to give to the consumer an oil containing quantities of up to only 0.1 per cent by weight of the itaconate polymers.

The antifoaming effect of the present polymers is not materially affected by the presence of other adjuvants in the oils. The polymers are stable esters which can be hydrolyzed only with ditliculty and since they are present in the oils in only very small quantities, the use of even very acidic or very basic adjuvants in the oil has substantially no elfect on them. Hydrocarbon oils containing the present antifoaming agents are stable when stored over long periods of time and also when subjected to heat and pressure conditions of engine and motor operation.

Hydrocarbon oils which are rendered substantially antifoaming by the present itaconate polymers are synthetic or petroleum stocks of varying viscosities such as lubricating oils for internal combustion engines and motors, diesel fuels and lubricants, and pressure transfer media, e. g., industrial lubricants, process oils, hydraulic oils, turbine oils, cutting oils, fluid greases, gear oils, shock absorber oils, spindle oils, journal bearing oils, pneumatic tool lubricants, etc. They may be synthetic or natural hydrocarbons or any type, i. e., paraffinic naphthenic or blended, and they may be compounded or uncompounded.

This invention is further illustrated, but not limited, by the following examples:

Example 1 This example describes preparation of polymeric di-nbutyl itaconate.

A mixture consisting of 243 g. of di-n-butyl itaconate and 2.5 ml. of di-tert-butyl peroxide was heated, with stirring, in a nitrogen atmosphere to a temperature of 160 C. within minutes and then maintained at about this temperature for about 1.5 hours. An additional 2.5 ml. portion of the peroxide was then added, and heating was continued for another 3.75 hours. The resulting reaction mixture, n =1.4597, was submitted to distillation at a pressure of 1 mm. of mercury in a nitrogen atmosphere. Material boiling at below 230 C./1 mm. was removed and there was obtained as a residue 154.1 g. of polymeric di-n-butyl itaconate, a viscous, light amber material, n =1.465l.

Example 2 The antifoaming properties of hydrocarbon oils may be determined according to the procedure generally described in Designation L-12445 of the Coordinating Lubricants Research Committee of the Coordinating Research Council, New York. Briefly this procedure involves bubbling air or an inert gas such as nitrogen through the hydrocarbon oil to be tested employing standard apparatus and standard conditions.

The oil was placed in a standard 100 cc. graduated cylinder in the top of which was inserted a two-hole rubber stopper. An air-inlet tube extended through this stopper, to the bottom of which was attached a gas difiuser stone sphere. The length of the inlet tube was adjusted so that when the apparatus was assembled, the sphere just touched the bottom of the cylinder.

Dry nitrogen was supplied at the rate of 0.2 cubic foot per hour, at room temperature. Thirty-seven cubic centimeters of a Champlin S. A. E. base oil was used for each test.

With the nitrogen hose disconnected between the flowmeter and the delivery tube to the difiuser stone, the stone was allowed to soak in the oil for five minutes, at the end of which time nitrogen flow (0.2 cu. ft. per hour) was started through the stone. Zero time was noted when the air bubbles started to rise from the stone. Readings of the top and bottom foam levels were taken at the end of a 5-minute period. The volume of foam was calculated from the two readings.

Employing the testing procedure described above, there was determined the antifoaming efiect of the polymeric n-butyl itaconate of Example 1 when added to the Champlin S. A. E. 30 base oil at concentrations of from 33 to 1000 parts per million. The following results were ob- Inasmuch as polymeric butyl or amyl itaconates are extremely eflicient antifoaming agents, polymers prepared from these itaconates and small amounts, say, up to 20 per cent of other monomers copolymerizable therewith, may also be used for depressing the foam-susceptibility of hydrocarbon oil compositions. 150, instead of polymeric butyl itaconate or polymeric amyl itaconate, there may be employed as antifoamants copolymers of two different alkyl itaconates present in such proportions and of such a nature as to give in the copolymer molecule an alkyl chain length of from 4 to 5 carbon atoms.

What we claim is:

1. A substantially foam-resisting hydrocarbon oil composition containing up to 1.0 per cent by weight, based on the weight of the composition, of homo polymeric di-nbutyl itaconate.

2. A substantially foam resisting hydrocarbon oil lubricant composition containing a hydrocarbon oil, and up to 1.0 per cent by weight, based on the weight of the composition, of homo polymeric di-n-butyl itaconate.

References Cited in the file of this patent UNITED STATES PATENTS 2,279,881 DAlelio Apr. 14, 1942 2,616,849 Grammaria Nov. 4, 1952 2,637,698 Tutwiler May 5, 1953 FOREIGN PATENTS 666,990 Great Britain Feb. 20, 1952 

1. A SUBSTANTIALY FOAM-RESISTING HYDROCARBON OIL COMPOSITION CONTAINING UP TO 1.0 PER CENT BY WEIGHT, BASED ON THE WEIGHT OF THE COMPOSITION, OF HOMO POLYMERIC DI-N BUTYL ITACONATE. 